#define  _CRT_SECURE_NO_WARNINGS 1	
#include<stdio.h>
int main() {
    int n = 0;
    int num = 0;
    int ret = 0;
    scanf("%d", &n);
    for (int i = 0; i < n; ++i) {
        scanf("%d", &num);
        ret ^= num;
    }
    printf("%d", ret);
}